ST. PAUL, Minn. - Just six months after Minnesota voters turned back an effort to ban gay weddings, lawmakers are poised to make the state the first in the Midwest to pass a law allowing them.

The startling shift comes amid a rapid evolution of public opinion nationally in the debate over marriage. But with Minnesota and possibly Illinois set to broaden the definition to include same-sex couples, coastal states may soon have some company in enacting changes.

In November, voters unexpectedly defeated a measure that would have banned same-sex marriage in the Minnesota Constitution, even after more than two-dozen states passed similar bans. That prompted gay marriage supporters to quickly go on offense.

Those efforts culminate Thursday with a vote in the state House that Democratic leaders assured would pass. With the state Senate expected to follow suit, Democratic Gov. Mark Dayton could sign a bill as early as next week.

"We like to lead the way in Minnesota," said state Rep. Karen Clark, the Minneapolis Democrat sponsoring the bill.

In the past week, Rhode Island and Delaware became the 10th and 11th states to approve gay marriage. But so far, only legislatures in coastal or New England states have voted affirmatively for gay marriage. Except for Iowa, which allows gay marriage due to a 2009 judicial ruling, same-sex couples can't get married in flyover country.

Minnesota might go first, but Illinois could be close behind. The state Senate there voted in February to allow same-sex marriage, and supporters think they're close to securing the votes needed to get it through the House and on to Democratic Gov. Pat Quinn, who says he'll sign it.

Although a few Republican politicians around the country have started to embrace gay marriage, the movement remains largely contained to states with Democrats fully in control. In the Midwest, only Illinois and Minnesota have Democratic-led statehouses. Democrats run the Nevada and New Mexico legislatures, but Republicans are governor in those states.

Democrats also control Colorado, but that state could only go as far as civil unions because of a constitutional amendment that blocks gay marriage. The same curb applies in Oregon, but a group has launched a drive to repeal the earlier ballot initiative.

Elsewhere, the political dominance of Republicans makes legalized gay marriage a difficult sell. Most of Minnesota's regional neighbors - Michigan, Wisconsin and both Dakotas - have entirely Republican power structures.

So far, only one Republican member of Minnesota's Legislature is a definite yes on gay marriage. But with the House vote looming Wednesday, the bill's backers said they would accept a handful of GOP-sponsored religious protections that could help them win over a few more Republicans.

Last fall's defeat of the gay marriage ban ended a nearly decade-long push by social conservatives for stronger prohibitions on gay marriage.

But the massive activist and fundraising network built to defeat the amendment has now been harnessed to get it through the Legislature.

"Our opponents did us a huge favor," said Sen. Scott Dibble, the bill's Senate sponsor. "They really accelerated the whole issue."

Dibble and Clark are both gay. First elected in 1986, Clark says she's the longest-serving lesbian state lawmaker in the country. She first introduced a bill to legalize gay marriage in 1998, just a year after her colleagues approved a state law defining marriage as between a man and a woman. Dibble's Senate district, anchored in the city's trendy Uptown area, had the highest number of gay couples in Minnesota in both the 2000 and 2010 census.

It was the heavily populated Twin Cities area that delivered most of the votes against the constitutional gay marriage ban - making it part of the first electoral victories on gay marriage last November after years of losses. But the ban got huge support from more rural parts of the state, populated with higher concentrations of seniors, religious and socially conservative voters.

That's left gay marriage opponents to argue that the legislative push now underway is a case of pushing big-city values on small-town residents.

"The metro area shouldn't be allowed to force gay marriage on the rest of the state," read the flyer for a rally sponsored by Minnesota for Marriage, the chief lobbying group against the ban.

But in recent days, a handful of House and Senate Democrats from rural districts have announced plans to vote for the bill. Rep. Joe Radinovich, a 27-year-old freshman Democrat from the central Minnesota town of Crosby, acknowledged he would alienate some constituents when he votes for gay marriage.

'"I know there are people who voted for me last year that won't vote for me next year because of this," said Radinovich, who beat his Republican opponent by just 323 votes. "But I'm not going to start my political career by voting 'no' on something I know in my heart that I support."

Associated Press reporters Brian Bakst in St. Paul and Sophia Tareen in Chicago contributed to this report.